#include<stdio.h>
struct node
{
    int val;
    struct node *next_ptr;
    struct node *previous_ptr;
};
main()
{
    struct node nd1,nd2,nd3,nd4;
    nd1.val=10;
    nd1.next_ptr=&nd2;
    nd2.val=20;
    nd2.next_ptr=&nd3;
    nd3.val=24;
    nd3.next_ptr=&nd4;
    nd4.val=50;
    nd4.next_ptr=NULL;
    nd4.previous_ptr=&nd3;
    nd3.previous_ptr=&nd2;
    nd2.previous_ptr=&nd1;
    nd1.previous_ptr=NULL;
    printf("the link list are %d %d %d %d \n",nd1.val,nd2.val,nd3.val,nd4.val);
}
